SAMPLING SOUNDS THE CHEETAH WAY

At last I have obtained a copy of Cheetah’s new Sound
Sampler. This is a music add-on for the Spectrum; like its predecessor,
the SpecDrum, the new gadget promises to be great fun for
non-musicians as well as budding pop stars.

Sound sampling is a simple idea. Like a cine camera taking pictures very
quickly, a sound sampler tests the volume of a sound literally tens of
thousands of times a second, and stores the result as a stream of numbers in
computer memory. The numbers can later be ‘played back’ through an
interface and loudspeaker, reproducing the original sound.

The faster you can read numbers, and the more accurately you can measure
volume, the better the sound quality. Good compact disc players can recognise
65,536 volume levels about 40,000 times a second; if it wasn’t for the
limitations of the recording equipment — ultimately, the microphones and
pickups — this would sound just like the real thing.

Cheetah’s sampler can discern 256 levels 35,000 times a second, so the
sound quality is a little rough and distorted, but has quite a wide tonal
range. The first pre-production unit I tested crackled badly, but Cheetah have
convinced me that this was a random fault on that hand-built prototype —
the second unit worked fine. A similar sampler, made-to-measure for musicians
on a budget, would cost about £200 and you couldn’t play games on
it!

A sound sampler can do many things that a tape cannot, as anyone who has
heard Paul Hardcastle’s NuNuNuNineteen hit will realise. In fact
that record only contains a tiny fraction of the repertoire of a good sampler.
And it’s easy. And it’s fun, for anyone remotely interested in
music.

THE PROSPECT

Almost everyone has musical ideas. Whether you hum, clap or tap
biros on a desk you probably make your own music from time to time. But, until
quite recently, you couldn’t produce ‘real’ music that way.
It took years of practice and training to be able to get ‘musical’
results out of the clumsy, tangled machines we call musical instruments. It was
boring, especially if you were forced to play other people’s music while
learning. Few people started to learn; most of them gave up. The world is full
of people with musical ideas who can’t express them. Yet.

There is a new revolution, happening in music. For the first time ordinary
people are discovering that they can make music acceptable to themselves and to
many others — without having to master the techniques of music or of
playing an instrument.

Once a sound has been stored in a computer it can be modified in a virtually
infinite number of ways; all you need is appropriate software. Of course, older
technology lets you alter sounds too, but the computer allows changes to be
recorded, replayed, tweaked, and tested in a totally reliable, repeatable
way.

Like other HiTech revolutions before it, the computer revolution in music
will not create anything new, but it will give everyone access to an ability
that previously was only available to a trained few.

The CheetahSound Sampler is an important step towards this new
musical world. It’s not a revolution in itself, but it is a sign of the
times, which is why I have spent a few paragraphs explaining what is going on.
This review will be from the point of view of a non-musician. Professional Muso
Jon Bates will add his comments next month.

THE PRODUCT

The box with two twiddly knobs, known to its f..f..f..friends
as the Cheetah Sound Sampler

£44.95 gets you a cardboard box containing a microphone,
interface unit, tape and manual. The microphone appears to have come from a
cheap cassette recorder — there’s even a tape-stop switch, although
the sampler makes no use of this. The quality of the microphone is adequate,
but it you’ve got a better one, use it.

The interface plugs into the edge connector at the back of your computer.
There’s no through port, so you can’t plug anything into the back
of the sampler. Two control knobs point back towards the Spectrum; you’ll
need some kind of bus extender if you want to use this interface with a deep
add-on keyboard such as a FullerFDS.

There’s a 3.5mm input socket on one side of the box and a trailing
output lead, ending in a phono plug, on the other side. This plugs into your
amplifier or HiFi, so that you can hear what you’re doing.

The electronics look well designed, although some of the soldering was a bit
dodgy on the prototypes I examined. Cheetah have used standard Ferranti chips,
with a metal ‘ground plane’ on the board to reduce interference
from the computer. Port 127 is used for input and output. You must access port
191 — the strobe — at least seven microseconds before you read a
sample, to trigger the analogue to digital converter.

The tape is the most important part of the package — software
determines the power of any computer-controlled musical device. One side of the
tape holds two programs — the Sampler and the Sound
Utilities. On the other side you find Samples — data recordings of
the sound of an organ, glass breaking, bells, a handclap, and speech. There are
no back-up recordings on the tape, but fortunately the files are easily copied;
they’re useless without the interface, of course. The manual is a
twelve-page cassette-sized booklet. The blue type is very small, but readable.
The text is interesting to read, but a little chaotic in organisation. There
are a few Hints and Tips, but not enough. For more, read on!

SAMPLER

The sampler loads from cassette in 2 minutes 40 seconds. After
the first part loads you must stop the tape and indicate whether or not you
want to transfer everything to Microdrive. This gets irritating if you’ve
only got tapes, although it is good to see that Cheetah are supporting the
Microdrive. The program also allows you to use the 128’s extra memory to
store samples — hooray!

Your first step should be to set the input level. I tested the sampler
successfully with microphones, a guitar, synth, cassette and compact disk. In
each case you connect the device to the small socket on the left of the
sampler, select the ‘Set Level’ option, and play some music or make
a noise. The graph of the sound appears on the screen. The display is re-drawn
every second, and looks quite pretty.

You must adjust the input level — the left hand knob — until the
graph fills most of the display without running into the top or bottom edge.
That indicates an overload, which would cause a distorted recording.

Once you’ve set the level you can use the sample menu. A standard
Spectrum can record about a second of good quality sound — or two seconds
at ‘half speed’, which gives a duller tone. Spectrum 128 owners can
record for up to six seconds — sampling uses up RAM at a prodigious
rate.

Memory is divided into small units and you can split these between named
samples as you wish. It’s a good idea to keep the sample names short, as
the software asks you for them rather persistently. Beware: the program does
not complain if you use the same name for more than one sample.

Once you’ve decided the length and speed of a sample you can start
recording under manual or automatic control. Manual recordings begin when you
press a key; automatic ones start as soon as the input signal reaches a fairly
high level. Immediately after recording you can hear what’s stored by
using the ‘List Samples’ option, which displays the name and length
of stored sounds, playing them back as they are listed.

Configuring a sound in the Cheetah Sampler’s edit
section... This is what “OY CAM” sounds like!

CONFIGURATION

To get full control you must use the ‘Edit’
sub-menu. This lets you combine, copy, reverse, or delete samples by name. Most
importantly, you can ‘configure’ a sound. This is a powerful but
rather fiddly process. The idea is to put down four markers, which between them
allow you to stretch sounds and get distinctive “NuNuNuNineteen”
effects.

As you configure a sound, each unit of the recording is displayed as a graph
on the screen. You can move to any point in the sound and position markers on
the graph at that point.

The graph corresponds directly to the sound, so you can spot the key points
by eye with a little practice. It takes a while to learn to do this, but the
final version of the software allows you to replay the sound up to and from the
current point, which makes it easy to find your way around by ear.

The four markers must be arranged in order. The first one indicates the
point where you want replay to begin. The sound is replayed from there, past
the second marker, and up to the third. If the control key is still held down,
the sound between the second and third markers is repeated. Otherwise the rest
of the sound — up to the last marker — is replayed, then the
computer stops till you press another key.

For example, you might sample the word “Cheetah”, putting the
first and last markers at either end of the word. If you put the second and
third markers around the ‘hee’ part of the word, a long stab at the
key would give the sound: “Chee-hee-hee-tah”. If you put those
markers nearer the end of the word, you might get
“Cheeta-ta-tah”.

There was no way to free the unused space at either end of a marked sound on
the software I tested. The final version should allow this.

Of course, you’re not stuck with speech. You can record screams,
crashes, bleeps, creaks, or any other sound. If you can’t afford a
synthesiser you can borrow one and sample it, saving the result on tape or
Microdrive for future use. Cheetah supply a few pre-recorded samples, but
it’s easy to record your own — I lost no time in blasting my
neighbours with sampled drum sounds from Cameo’s recent hit
The word UP!

The playback option is controlled by twelve keys, each corresponding to a
different note in a piano-key arrangement. In conjunction with SHIFT you can
replay a sample at any one of 24 different pitches, higher or lower than the
original. The Art of Noise like to do this sort of thing.

Unfortunately the speed of playback changes with the pitch, so it is hard to
use musical samples containing more than one beat. Pure notes from other
instruments usually sound okay, as you can fill them out by repeating a
section.

The save and load options seemed to work fine; they allowed you to delete
and catalogue Microdrive files, but there was no option to format a new
cartridge. The sampler may seem hard to use, and indeed the menu structure is a
bit irritating at times, but it’s not long before you can find your way
around. From then on it’s f... f... f... fabulous, whether you’re
just playing around or trying to get a specific effect.

SOUND UTILITIES

The Sound Sampler contains electronics to read sounds
and replay them — and it can do both at the same time, delaying or
adjusting the levels to produce an incredible range of effects. The Sound
Utilities are provided by a small machine-code program recorded after the
Sampler. Tape loading time is about one minute.

The Utilities can process sounds in lots of different ways, and sometimes
the names of the options don’t really match up with the effect. Rather
than try to analyse what the program is doing, I’ve chosen to describe
the sound. Readers who are not familiar with BBC Science Fiction may find some
of the analogies a bit puzzling!

There’s no level meter in this package, so you must set the input
level — the left hand knob — by listening for distortion. All of
the effects produce results which you can hear at once, so this is not much of
a problem. The main menu lists six options — an Echo Chamber, Reverb
Unit, Pitch Shifter, Fuzz Box, Sound Chopper and ‘Bubbleizer’. Most
options have one or two ‘slider controls’ associated with them.
When an option is selected, the appropriate control keys are displayed until
another key is pressed — a nice feature. You can’t use a mouse or a
joystick, unfortunately.

The Echo Chamber produces a good artificial echo effect, like a
Kopykat tape echo machine. It is fun, and good practice for public
speaking, to wear headphones and try to talk while a recording of what you said
half a second before is played back, full blast. The right hand knob on the
interface comes into play here, controlling the extent to which echoes are
themselves echoed. Setting this to maximum and using the longest echo you get
three or four echoes of each sound, fading over about two seconds, with the
last one very quiet and distorted.

The minimum echo setting produces the acoustics of a small toilet with a
high ceiling. Prehistoric pop-pickers will remember that the Korgis
recorded their No.13 hit If I had yoooooo in the loo to get just this
sound — now it’s built into your Spectrum!

The Reverb Unit is meant to produce a more natural echo. In fact it produces
a quite unreal effect. At low settings it adds echo and an interesting tuned
Jew’s Harp sound buzzing in time with your voice. I used the microphone
with this effect, and the result sounded a bit like a Vogon Laurie
Anderson (Oh SuperVogon?).

As you increase the setting, the sampler just seems to pick notes randomly
from the input — speech remains inflected but is unintelligible once the
control is about half way across the scale. At the top setting you just get a
pipelike fuzzy wailing tone in time with your voice.

The Pitch Shifter could be dedicated to Douglas Adams’
Hitchhikers Guide to the Galaxy since many of the voices from the
series are here. The effect is to shift the pitch of the input in a rather
unsteady way, up or downwards. At the top of the scale a voice sounds like a
Magrathean Mouse. Lower down there are all sorts of voices: ‘Toff’,
‘Brummie’, ‘TV-Voiceover’, ‘Marvin the Paranoid
Android’ and a good (?) ‘Vogon’. Use the second control
— the ‘duty cycle’ to search for each of the above as you
reduce the pitch. There are lots of other effects I can’t describe.

The Fuzz Box is rather trivial. Whatever signal is put in, it limits the
output to a fixed maximum level. Loud sounds are distorted — the louder,
the more distorted. There’s no control — just a ‘quit’
key. Quit.

The Sound Chopper seems to be the favorite at Cheetah. Throughout the PCW
show, from their position on the balcony, they shouted in imitation Dalek tones
as I scuttled around talking to people. The sound chopper produces a very
authentic Dalek voice from a human monotone. It works by chopping the sound up
and only replaying alternate parts.

Slightly slower settings work well on synthesisers and guitars, especially
if you use Stereo or mix in a bit of the un-chopped signal. The slowest
settings are pretty useless, and the control moves very slowly — the
longest chop time is about two thirds of a second, and the slider only moves a
small distance every chop.

The strangely-spelt Bubbleizer is a new effect invented by Bob Powell
of Speedwell Software. Bob designed the Sound Sampler for Cheetah. The
Bubbleizer starts out sounding as if a Kazzoo band is playing along with your
voice (or whatever else you’re recording). Greater settings add a
metallic rasp, and a kind of dripping hollow echo, rising in pitch.

After a while the noise becomes abstract, and sounds like a sympathetic
Sci-Fi whistling computer; a collection of short, pure tones in time with the
input. This gets slower and slower. If you hum, at the maximum setting, the
result resembles some kind of alien police siren. The Depth control works
painfully slowly here — it takes 40 seconds of
‘auto-repeating’ to move it across the scale.

UTILITIES SOUND

I suspect that this program was included for musicians. In fact
it has so many effects that it will probably produce music for anyone who can
hum. Instruments — who needs ’em?

I looked at two prototype versions of this sampler. The first was abnormally
noisy and there were a few ‘rough edges’ in the software, but the
problems were irritations rather than major flaws. I’m fairly sure that
both hardware and software will be tidied up by the time you read this and
Cheetah are in mass production.

Cheetah have two more products in the pipeline — a sequencer, which
can automatically play tunes made up of sampled sounds, and a mega-clever
bi-directional MIDI interface. Datel and RAM Electronics are also addressing
this musical market. It’s good that they’re taking Spectrum users
with them!